Mathutils Vector Raycast
I know this is old but had to work on a similar situation tonight.

All you need to do is add the vector to your 3D point A(which should also be a vector pointing from your object to the origin point of the scene). This should give you a target point in 3D space.

target_point = point_A.worldPosition + vector


If you want to change the distance away from your point_A origin, you need only alter the magnitude of your vector:

vector.magnitude *= 5 # 5 times the vector length


or

vector.magnitude += 30 # 30 Blender units greater than your original vector